The invention relates generally to heat dissipation electronic circuitry and more particularly to an improved thermal core material used as a heat spreader for printed wiring boards (PWBs) and other electrical and electronic assemblies.
Heat dissipation for electronic devices and components mounted on printed wiring boards (PWBs) having a low thermal conductivity (˜0.3 W/mK) is a growing problem as device/component power consumption increases to meet escalating performance requirements. Metal-core printed wiring boards (MCPWBs) in which 900-3,500 μm (30-135 mil) thick copper or some other conductive metal sheet is embedded/laminated between glass-reinforced epoxy boards (for example G10 or FR-4) is a possible solution. The embedded conductive metal acts as a heat channel or spreader assisting heat distribution over a larger area for faster dissipation.
However, the use of such thick metal conductors like copper adds significant weight, approximately 7-30 kg/m2 (22-100 oz/ft2) to the PWB. For a typical 1.6 mm ( 1/16″) thick G10 PWB this amounts to 2-10× increase in circuit board weight. The extra weight is a serious issue for weight-restricted air- and spacecraft electronic payload applications. There is strong incentive to use lighter weight thermal conducting core materials such as aluminum or graphene sheet. However these materials have other issues; aluminum has half the conductivity of copper so thicker sheet material is required and graphene sheet has anisotropic conductivity properties. In other words, while thermal conductivity in the x-y plane of a graphene sheet is typically Kxy 200-500 W/mK and Kz only 3-6 W/mK).
Thus, a need exists for heat spreading core materials for PWBs with improved thermal performance and lighter weight.